It should behave mostly identically to the current release (version
4.1), but the version number bump reflects a significant change in the
code: it was reshuffled to use fewer files, and it indentation code was
completely rewritten to use the SMIE engine which provides generic
indentation and navigation support.
The use of SMIE brings a few side-benefits: blink-paren matching of
things like let..end (requires Emacs≥24); auto-fill-mode can choose good
places to cut a line (upcoming in Emacs-24.2); and yet more to come.
On emacsen that do not come with SMIE, sml-mode will automatically
fallback on the old indentation code (stashed in sml-oldindent.el).
Changes since 4.1:
* New indentation code using SMIE when available.
* `sml-back-to-outer-indent' is now on S-tab (aka `backtab') rather than M-tab.
* Support for electric-layout-mode and electric-indent-mode.